Thermopolarization Phenomena in the Temperature Range of Glass Transition of Amorphous Polydiethylsiloxane

2018 ◽  
Vol 773 ◽  
pp. 15-19
Author(s):  
I.V. Popov
Keyword(s):  
Glass Transition ◽  
Amorphous Phase ◽  
Elastic State ◽  
Structural Units ◽  
Flexible Chain ◽  
Experimental Conditions ◽  
Temperature Range ◽  
Maximum Value ◽  
Temperature Dependences ◽  
Amorphous Phase Formation

The transition from the glass to the highly elastic state in polydiethylsiloxane (PDES) is not reflected on the temperature dependences of the relative permittivity, the dielectric loss tangent, and the specific volumetric electrical conductivity. But, the peak of the current of thermostimulated depolarization (TSD) is fixed in the temperature range of the transition to the highly elastic state. The peak of the TSD current at T ~ 130K indicates a continuous amorphous phase formation in the experimental conditions. The maximum value of the TSD current directly depends on the content of the amorphous phase in the polymer. The cooling of the polymer in an electric field reduces the magnitude of the peak. Exposure in the mesophase leads to an almost complete absence of thermopolarization effects near the glass transition temperature. This peak of the TSD current in the absence of preliminary polarization is characteristic, presumably, only for flexible-chain polymers where structural units have pyroelectric properties. Under certain conditions, PDES demonstrates itself as an active dielectric in the temperature range of 90 - 180K.

The influence of crystalline texture on the tensile properties of natural rubber. I

1974 ◽  
Vol 338 (1615) ◽  
pp. 459-478 ◽  
Keyword(s):  
Glass Transition ◽  
Natural Rubber ◽  
Tensile Properties ◽  
Amorphous Phase ◽  
Crystalline Phase ◽  
Full Range ◽  
Glassy Matrix ◽  
Tensile Behaviour ◽  
Crystalline Morphology ◽  
Temperature Range

The crystalline morphologies that are attainable in samples of natural rubber (n. r.), by extending the samples prior to crystallization, are reviewed. Specimens covering the full range of crystalline morphologies possible have been prepared and tensile tested between – 120 and – 26 °C. The tensile behaviour of crystalline samples is compared and contrasted with that of oriented, but non-crystalline, identical natural rubber in the same temperature range. It is found that the tensile behaviour of semi-crystalline n. r. is dominated by the amorphous phase throughout the temperature range – 120 to – 26 °C. At temperatures above the glass transition temperature ( T g ) of the amorphous phase, the crystalline phase acts mainly as a diluent of the amorphous phase. At temperatures below T g , where the crystalline phase is set in a glassy matrix, it is found that the crystalline morphology does significantly affect the tensile behaviour. Attempts are made to differentiate the effects of crystallinity, crystalline morphology and orientation of the amorphous phase on the tensile properties of natural rubber.

An NMR solid-echo Study of Guanidinium Cation Reorientation in [C(NH2)3]3Sb2Cl9

2004 ◽  
Vol 59 (11) ◽  
pp. 787-790
Author(s):  
P. Bilski ◽  
M. Olszewskia ◽  
N. A. Sergeev ◽  
J. Wa̻sicki
Keyword(s):  
Wide Temperature Range ◽  
Temperature Range ◽  
Temperature Dependences ◽  
Time Position ◽  
Nmr Solid ◽  
Guanidinium Cation

The NMR solid-echo polycrystalline tris-guanidinium nonachlorodiantimonate (III) has been studied in a wide temperature range. The temperature dependences of a time position and an amplitude of solid-echo are characterized by minima at ca. 143 K and 273 K, which are assigned to the reorientation of two dynamically inequivalent guanidinium cations [C(NH2)3]+. The motional parameters of the two types of guanidinium cations have been determined. -PACS: 64.70K; 76.60.E

Amorphous phase formation in irradiated intermetallic compounds

1983 ◽  
Vol 77 (3-4) ◽  
pp. 273-293 ◽  
Author(s):  
J. L. Brimhall ◽  
H. E. Kissinger ◽  
L. A. Charlot
Keyword(s):  
Intermetallic Compounds ◽  
Amorphous Phase ◽  
Phase Formation ◽  
Amorphous Phase Formation

Amorphous Phase Formation During Ion Mixing of Ti/Si Bilayers at Elevated Temperature

1988 ◽  
Vol 100 ◽  
Author(s):  
K. Maex ◽  
R. F. De Keersmaecker ◽  
M. Van rossum ◽  
W. F. Van Der Weg
Keyword(s):  
Elevated Temperature ◽  
Thermal Treatment ◽  
Diffusion Couple ◽  
Amorphous Phase ◽  
Phase Formation ◽  
Multilayer Structure ◽  
Elevated Temperatures ◽  
Binary Diffusion ◽  
Amorphous Phase Formation

ABSTRACTThe amorphous phaseformation in Ti-Si bilayers upon ion mixing at elevated temperatures and in Ti-Si multilayers upon thermal treatment was studied. In the case of ion mixing with 5×1015 cm−2 Xe atoms at temperatures around 240°C a 100nm thick amorphous Ti-Si alloy is formed with a very homogeneous Ti:Si=3 :4 composition. Thermal treatment of the Ti-Si multilayer structure at similar temperatures also yields amorphous silicide layers. The results are interpreted according to the evolution in a planar binary diffusion couple, where the Si and Ti concentrations in the reacted layer are dictated by thermodynamic and kinetic arguments.

scholarly journals Описание колоссального магнитосопротивления La-=SUB=-1.2-=/SUB=-Sr-=SUB=-1.8-=/SUB=-Mn-=SUB=-2-=/SUB=-O-=SUB=-7-=/SUB=- на основе "спин-поляронного" и "ориентационного" механизмов проводимости в парамагнитной области температур

2020 ◽  
Vol 62 (5) ◽  
pp. 669
Author(s):  
С.А. Гудин ◽  
Н.И. Солин
Keyword(s):  
Magnetic Field ◽  
Colossal Magnetoresistance ◽  
Main Role ◽  
Spin Polaron ◽  
Temperature Range ◽  
Conduction Mechanisms ◽  
Theoretical Investigations ◽  
Temperature Dependences ◽  
The Magnetic Field ◽  
Good Agreement

Experimental and theoretical investigations of the resistance of the La1.2Sr1.8Mn2O7 single crystal in magnetic fields from 0 to 90 kOe and in the temperature range from 75 to 300 K has been studied. The magnetoresistance is determined by the “spin-polaron” and “orientation” conduction mechanisms. Using the method of separating contributions to the magnetoresistance from several conduction mechanisms, the observed magnetoresistance of La1.2Sr1.8Mn2O7 manganite in the temperature range of 75-300 K is described, good agreement between the calculated and experimental data is obtained. In a magnetic field of 0 and 90 kOe, the temperature dependences of the size of the spin polaron (in relative units) are calculated for the temperature range 75–300 K. It is shown, that the КМС value is determined by an increase in the linear size of the spin polaron (along the magnetic field), i.e. the main role in the magnitude of the colossal magnetoresistance is made by the change in the size of the magnetic inhomogeneities of the crystal.

Study of the microstructure of low-molecular rubbers

2021 ◽  
Vol 87 (11) ◽  
pp. 26-32
Author(s):  
A. A. Pushkareva ◽  
O. A. Vozisova ◽  
M. A. Leuhina ◽  
L. L. Khimenko ◽  
A. N. Ilyin ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Glass Transition ◽  
Comparative Analysis ◽  
Low Temperature ◽  
Ir Spectroscopy ◽  
Rheological Properties ◽  
Polymer Chain ◽  
Epoxy Oligomer ◽  
Hydroxyl Groups ◽  
Structural Units

The oligomer microstructure, reflecting the configuration of the elementary units (cis-1,4-, trans-1,4-, and 1,2-) and their distribution order in the polymer chain, decisively affects the physicochemical and rheological properties of the oligomer. Parameters of microstructure-dependent transitions (glass transition) characterize the oligomer behavior under abnormal low-temperature conditions. We present the results of studying the microstructure of low-molecular rubbers. We determined the content of cis-1,4- and trans-1,4-structural links of poly-divinyl-isoprene-urethane-epoxy oligomer. The structure of polybutadiene HTPB-IV with terminal hydroxyl groups was analyzed using NMR and IR spectroscopy. A comparative analysis of the microstructure of the poly-divinyl-isoprene-urethane-epoxy oligomer and low molecular rubbers with a known content of structural units has been carried out. The obtained results can be used to obtain oligomers with the desired physicochemical and mechanical properties.

Temperature dependence of the resistance, impedance and capacitance of semitransparent PTB7-Th and PCBM sensor

2019 ◽  
Vol 33 (12) ◽  
pp. 1950110
Author(s):  
Muhammad Riaz ◽  
Khasan S. Karimov ◽  
Jameel-Un Nabi
Keyword(s):  
Light Intensity ◽  
Temperature Dependence ◽  
Temperature Sensor ◽  
Visual Control ◽  
Capacitance Measurement ◽  
Experimental Conditions ◽  
Temperature Resistance ◽  
Graphene Composite ◽  
Temperature Dependences ◽  
Resistance Coefficients

The temperature dependences of resistance, impedance and capacitance of semitransparent sensor having structure ITO/PTB7-Th:PC[Formula: see text]BM/Graphene composite (semisurface type) were investigated. The transparency of the sensor was 58–60%. The dependences of the resistance, impedance and capacitance at different frequencies 100 Hz, 1 kHz, 10 kHz, 100 kHz and 200 kHz and temperature in the range of 23.8–80[Formula: see text]C for the sensor were studied. It was observed that as the temperature increased from 23.8[Formula: see text]C to 80[Formula: see text]C, the resistance and impedance (at 1 kHz) of the samples decreased, on average, by a factor of 3.51 and 3.79, respectively. At same experimental conditions (1 kHz), the capacitances of the samples also decreased by a factor of 9.6. It was also noted that as frequency increased from 100 Hz to 200 kHz, the impedance of the sensor decreased by a factor of 21 and 12, at temperatures 24[Formula: see text]C and 58[Formula: see text]C, respectively. Under the same conditions, the capacitance decreased by a factor of 30 and 28, respectively. The temperature resistance coefficients were measured to be −1.31%/[Formula: see text]C, −1.30%/[Formula: see text]C, −1.27%/[Formula: see text]C, −0.84%/[Formula: see text]C, −0.72%/[Formula: see text]C and −0.33%/[Formula: see text]C for R, Z (100 Hz), Z (1 kHz), Z (10 kHz), Z (100 kHz) and Z (200 kHz), respectively. For capacitance measurement, the temperature capacitance coefficients were measured as −1.39%/[Formula: see text]C, −1.38%/[Formula: see text]C, −1.37%/[Formula: see text]C, −1.36%/[Formula: see text]C and −1.34%/[Formula: see text]C, respectively. The semitransparent PTB7-Th- and PC[Formula: see text]BM-based temperature sensor can be used for measurement of the temperature as a teaching aid in situations where visual control of illumination and light intensity is required.

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